Bai, Zhongze;
(2023)
Nitrogen Migration during Coal Splitting and Staging Process and Assisted Combustion: A Reactive Molecular Dynamics Study.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Coal splitting and staging is a potential approach for reducing nitrogen oxide (NOx) emissions during coal oxidation, which converts NOx into harmless gas (N2) using coal pyrolysis gas. The NOx removal behaviours in this process are determined by the nitrogenous species in pyrolysis gas. In the current work, reactive force field (ReaxFF) molecular dynamics (MD) is used to examine the pyrolysis process of nitrogenous compounds in coal and the NOx reduction by nitrogenous species from coal pyrolysis gas. The effects of water (an important component of coal) on pyridine (a main nitrogen-containing compound in coal) pyrolysis were studied. At different water-content circumstances, common and uncommon intermediates were found and identified. Water influenced both the amount of nitrogen atoms in the polycondensation product and the consuming rates of pyridine molecules. The modifications in reaction pathways brought on by the presence of water were illustrated as well. The efficiency of NO abatement with nitrogenous species in pyrolysis gas (HCN and NH3) was also studied in relation to temperature, oxygen content, nitrogen-containing species content, and nitrogen-free species (CH4, CO, and H2). The atomic-level reaction pathways for NO abatement and N2 generation were identified under varying conditions. Besides, the behaviours of NO abatement by HCN and NH3 under various circumstances were compared and control methods for the pyrolysis and reburning processes were suggested. Assisted combustion, where electric field (EF) and ozone are applied during coal combustion, is an effective method for NOx control. The influence of EF and ozone on fuel-NOx generation from pyridine (the main nitrogenous chemical in coal) oxidation were studied via ReaxFF MD simulations. The number of key products (CO, CO2, NO, NO2 and N2) were quantified for the pyridine oxidation under varying external electric field conditions and in the presence of ozone, respectively. The mechanisms of pyridine combustion with electric fields and ozone addition were revealed at atomic scales. In summary, this study provides new insights into the nitrogen migration during coal splitting and staging as well as assisted combustion. The new findings lay theoretical foundations for strategizing effective NOx control ways in practice.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Nitrogen Migration during Coal Splitting and Staging Process and Assisted Combustion: A Reactive Molecular Dynamics Study |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author's request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10168258 |
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